Electromagnetic device



Sept. 8, 1925.

M. cRMER ELECTROMAGNETIC DEVICE 2 Sheets-Sheet 1 Filed March 23, 1922InVenCov I Michel Cre'mef,

His bitter-n61) Patented Sept. 8, 1925. i

UNITED STATES?" PATENT OFFICE.

MICHEL CREMER, OF PARIS, FRANCE, ASSIGNOR 'lO GENERAL ELECTRIC COMPANY,A CORPORATION OF NEW YORK.

ELEOTROIEAGNE'I'IC DEVICE.

Application filed March 23, 1922.

To all whom it may concern."

Be it known that I, Mionnn Gunmen, a citizen of Russia, residing atParis, France, have invented certain new and'usetul Iniprovements inElectromagnetic Devices, oi which the following is a specification.

The electromagnetic device of the pres.

ent invention has a particular application as a relay for controllingthe automatic starting of an electric motor by means of separatelyactuated electromagnetic switches or contactors, and although not necesa rily limited thereto is particularly applicable to the starting ofasynchronous motors having a wound rotor. These contactors arecontrolled by the electromagnetic relay hereinafter described. Thepurpose of this relay as employed in the control or" an electric motoris to produce automatically the progressive energization of a number ofcontactors in a predetermined order, the energization of the cont actorsproceeding the decreasing starting current reaches a certain minimumvalue or in accordance with the acceleration of the motor. Thus thestarting operation is always produced at normal torque and theacceleration depends upon the load on the motor.

In the case of induction motors with wound rotor, it is not practical tostart by means of contactors without controlling-relays it being assumedthat the potential and the frequency of the rotor circuit are v2.-riable. The only practical means consists in the use of accelerationrelays, butin the starting systems generally in use, two are generallyused, one of which controls the even contactors and the other the oddones; from this arises a serious complication of the automatic startingoutfits, especially when the number of steps is small, since it isnecessary, for example, to have two relays to control three contac-tors.

The system, the description of which is given below, effects thestarting as a "function of the intensity of an asynchronous motor,controlling any number of contactors through a single and relativelysimple relay, the construction of which is based on the followingprinciple:

Instead of two relays, a single one is employed having two differentcontacts which are closed alternately. One of these con tacts suppliesthe attracting coils of the Serial No. 546,1 19.

even contactors, and the other produces the release of the oddcontactors. A series coil which is traversed by the principal current ofthe stator serves as a minimum-intensity coil; another fine-wire coil,connected to the potential of one phase serves to hold the movable partof the preceding coil and to commute the control-current by connectingit either to the first or to the second group of contactors. Due to thisprinciple, the order of release of the contactors cannot be changed,that is to say, contactor No. 1, for example, cannot be closed beforethe closure of contactor No. 3.

The characteristic features and the advantages of the invention will bebetter understood by referring to the following description anddrawings:

Fig. 1 represents a sectional elevation of the acceleration relay; Fig.2 is a diagram of the connections of the relay in the case which appliesto the automatic starting of an asynchronous motor with a wound rotor infour steps by means of a controller; Fig. 3 is also a diagram ofconnections, but modified with a view to a starting equipment for alow-power motor.

Referring to Fig. 1, the relay is composed of two separate magneticcircuits. The magnetic circuit 1 is excited by the series coil 2traversed by the principal current of one phase of the controlled motorstator. This magnetic circuit is closed by the armature 3 which ispivotally mounted at i, or by the armature 5 situated behind 33 andwhich turns about the shaft. 6. The regulable springs 7 and 8 tend torelease the two armatures. The second magnetic circuit 9, in the form ofa U, carries a shunt coil 10, supplied by the voltage of one phase ofthe source of supply. Its reciprocating plunger core 11 carries at thetop a guide rod12 of brass, with a regulable stop 13 and, at the bottom,another stop 14. hen the coil 10 is supplied with current, the core 11rises, and since the stop 1st causes the amature 5 to rotate, the latteris brought to a stop, closing the magnetic circuit 1. On the contrary,when the attracting circuit of the coil 10 is broken, the upper stop 13causes the arresting of the armature 3. The armatures carry two verticalblades with contact fingers 15 and 16, which establish respectively, atthe stationary contact 17, the

will;

release circuit of the even cont actors, and at the stationary contact18, that of the odd contaetors.

The operation of the relay will now be described, first in case 01"starting and then in case of stopping.

The diagram of connections oil the acceleration relay may be made inCGv'QlRl LlliliClfent ways. Fig. 2 represents one of the pos siblesolutions; it is provided for the automatic starting of an asynchronousmotor with wound rotor in four steps, by means of a control-switch.Assuming this diagram, the operation is as follows:

The. line switch 20 being closed, the contactor 21 is energized to closeand thereby energize the stator 38 of the motor by closing thecontrol-switch 19. This causes the establishing of the control-circuitthrough the fuse 25, the auxiliary contact 33 on the contactor 2 1-, theshunt coil 10 oil the relay and a protecting resistance Bel. At the sametime, the motor starts, all the starting resistance being interpolatedin the circuit oi? the rotor 39. The arn'iature ll of the shunt coil 10is then attracted, releasing the armature 3, because the stop 13-3lifted; but 3 cannot rotate, notwithstanding the tension of the spring7, because the starting current produces a strong attraction through theseries coil 2 and prevents the release ot the armature 3. At the sametime the armature 5 is arrested by the stop 14. ll hen the intensity otthe current which is passing through the coil 2 has returned to its minimum regulating value, in consequence oi? the acceleration of the motor,the armature 8 may be released, urged by the spring 7; it rotates,closingthe contacts lf'i li and causing the contactor to close. The attracting coil of the contactor 22 is supplied with current through theauxiliary contact 26. hen the contactor 22 closes the coil 10 of therelay is short circuit-ed through the auxiliary cont ct 30 of cont-actor23, auxiliary contact 27 ott'contactor and auxiliary contact 33 ofcontactor 24: The core 11 consequently falls, and holds by its stop 13,the armature At the same time the contactor 22 short-circuits theconnections of the first section oi resistances.

The armature 5, which is then released by the stop 14:, does not rotateuntil the current through the winding 2 has sufficiently diminished;after this it rotates to the right and closes, through the contacts 16and 18, the engaging-circuit of the contactor 23, which has beenprepared by the auxiliary contact 28 oi? the preceding contactor 22. Thecontactor 23 then closes and short circuits the next rotor resistor byclosing the connections 36.

The auxiliary contact 30 or the contactor 23 is opened by the closing ofthe conta :tor 23 and breaks the short-circuit around the coil 10, whichis consequently re-excited and its core 11 rises and holds the armature5 in the attracted position. The relay armature 8 is at the same timereleased; but it continues to be magnetically held in its positiou, dueto the third point of current intensity which is produced in consequenceoi the closing oi the contactor ll hcn the motor current again drops,the armature -3 is released and it closes, through the contacts l517,the circuit ol attraction oi? the contactor 24 which has been preparedby the closing of the auxiliary contact 31 of the contactor 23.

The contactor 2st, on making engagement, shmt-circuits, through thectmnections 3?, the entire starting resistance. ii maintaiir ing circuitfor the contactor Liis established tl'irough the contact 32 and thecircuit oil the coil 10 is interrupted at the auxiliary contact 33; therelay is then returned to its original position.

For stopping, the control-switch 19 is opened, which operation causesthe release oi the contactor 21 of the stator. The latter interrupts thecircuit of the stator and the control-circuit of all the othercontactors.

The regulation of the relay is produced independently for each armature,by means of the springs T and 8. Their tension regulated in such mannerthat the rel ase oil the armatures is effected at a certain minimumstarting current, thus causing the starting of the motor as a functionof the Value oi the motor current. Ii the motor starts at no load, itsacceleration is ell'ected mode rapidly, since the points of intensitydiminish rapidly; when the motor is loaded the starting operation iseffected less rapidly, especially when the motor has to accelerate alarge body.

In the preceding diagram each of the contactors 22 and has threesupplementary contacts, which is not at all a disadvantage when thecontactors are relatively large; but it the starting outlit is providedfor a motor of low power and small cont actors, it is necessary toreduce the number of these contacts per contactor, in order to simplifythe construction. Fig. 3 repre" sents the simplified diagram of controlcon-- nections which makes it possible to get an automatic startingoperation by means of four contactors with the reduced number o'lsiuiiplementary contactors.

The engagement of the contactor :2 l (stator) is effected by the closureof the switch 19. The control current passes through the fuse theauz-ailiary contact 24 of the contactor 2th. and it excites the shuntcoil 10 of the acceleration relay which is mounted in series with theprotective resistance 3d. The core 11 (see Fig. '1.) attracted; thearmature 5 consequently stopped; the armature- 3 remains attractor bythe coil 2 because of the current talren by the motor on the firststarting point. When this starting current diminishes, the armature 3closes the contacts 15-17, which causes the energization of thecontactor 22. Its auxiliary contact 22 short-circuits the coil 10 andfurnishes at the same time the holding current for the contactor, whileits second auxiliary contact 22 prepares the engagement circuit of thecontactor 23. The shunt coil 10 being short-circuited, its core falls,releasing the armature of the relay which, after a certain period oflag, is re leased and which produces, through the closure of thecontacts 161S, the engage-- ment of the contactor 23. The latter isprovided with two auxiliary contacts. The twodirections-contact 23interrupts to the right; consequently it interrupts the hold ing circuitof the contactor 22, which is released; it thus breaks the short-circuitof the coil and closes, to the left, the holding circuit of thecont-actor 23. The contact 28 prepares for the closure of the contactor2%. The coil 10, which is then re-excited, attracts its core, whichreleases the armature 3 of the relay. The latter, when the startingcurrent due to the closing of the contactor 23 has been decreased,energizes by the closure of the contacts 17, the last contactor 24, theauxiliary contact 24% of which interrupts the control circuit passingthrough the coil 10 and the preceding contactors 22 and 23. Theauxiliary contact 2& furnishes the holding current for the attractingcoil of the contactor 24. The motor is stopped in the same way asbefore, by opening the switch 19. This arrangement requires, for eachrotor contactor, only two suppleinentary contacts, which fact simplifiesthe auto matic starting of motors of low power by means of smallcontactors.

It will be seen that the invention has a particular application insystems in which at least three accelerating resistors and theircorresponding contaotors are provided, the system being particularlyapplicable to systems of control having three or more acceleratingcontactors.

In accordance with the provisions of the patent statutes of the UnitedStates, I have described the principle of operation of my invention,together with the apparatus which I now consider to represent the bestembodiment thereof; but I desire to have it understood that theapparatus shown is only illustrative, and that the invention can be canried out by other means.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,

1. An electromagnetic device comprising a series electromagnet and twoalternately operating switch members, each of which is movable from oneposition to a second position under the control thereof, and a shuntelectromagnet having a magnetic movable element which moves the saidswitch members alternately to their first respective positions to beunder the control of the series electromagnet and releases the switchmembers alternately to move to their respective second positions underthe control of said series electromagnet.

2. An electromagnetic device comprising a series electromagnet and twoalternately operated switch members, each of which is movable from oneposition to a second posi-' tion under the control thereof, and an alternately energized shunt electromagnet having a reciprocating magneticelement which is connected to the switch member to alternately operateone of the switch members and to hold the same in its respective firstposition and release the other switch member to move to its respectivesecond position under the control of the series electro1nagnet.

A relay for controlling electric motors comprising a serieselectromagnet, a plurality of magnetic movable members biased to theunattracted position controlled thereby, a pair of switch contactscontrolled by each of said members, and a shunt electromagnet foralternately holding one of the said pair of contacts at a time in theopen position.

4. A relay for controlling electric motors con'iprising a serieselectroinagnet, a plurality of nagnetic movable members biased to theunattracted position controlled thereby, a pair of switch contactsbiased to the closed position controlled by each of said members, and ashunt electroinagnet having a mag netic movable member for alternatelyholding one at a time of said pairs of contacts in the open position andits associated magnetic movable member of the series electromagnet inthe attracted position.

5. An electromagnetic relay comprising a series electromagnet and twopivotally mounted switch members biased to their respective closedpositions and movable to their respective closed positions under thecontrol of the series electromagnet, and a shunt electromagnet having areciprocating plunger, the ends of which cooperate with the switchmembers for alternately moving one switch member to and holding the samein the open position to be under the influence of the serieselectromagnet and releas-' ing the other switch member to move to theclosed position in accordance with its bias under the control of theseries electromagnet.

In witness whereof, I have hereunto set my hand March 7, 1922.

MICHEL CREMER.

